1. Field of the Invention
This invention relates to an image heating apparatus for heating an image on a recording material. The image heating apparatus can be used, for example, as a fixing apparatus for fixing an unfixed image on a recording material in a copying machine, a printer or the like.
2. Description of Related Art
In an image forming apparatus adopting an electrophotographic image forming process, there has heretofore been provided a fixing apparatus for heat-fixing an unfixed toner image on a recording material.
In recent years, from the viewpoints of quick start and energy saving, there has been put into practical use a fixing apparatus using a belt (see, for example, Japanese Patent Application Laid-open No. H04-44075).
Specifically, this fixing apparatus is of a construction in which a fixing belt is nipped between a ceramic heater and a pressure roller to thereby form a fixing nip, and a recording material is introduced into this fixing nip to thereby fix an unfixed toner image on the recording material.
Such a fixing apparatus using the belt does not require the supply of electric power to the heater on standby, and can be brought into a state in which it is capable of fixing before the recording material arrives at the fixing nip even if the supply of electric power to the heater is effected after the image forming apparatus has received a print signal. Consequently, it is excellent in that the time required for image formation can be shortened and also, consumed electric power can be reduced.
There has also been proposed a fixing apparatus in which a pressure pad is disposed so as to be opposed to a fixing roller with a belt interposed therebetween (see, for example, Japanese Patent Application Laid-open No. H10-186910).
In these fixing apparatuses using a belt, there is the possibility that the belt is biased toward a bus line and the conveyance of the recording material becomes unstable to thereby cause the recording material to be wrinkled.
So, against such a problem, there has been proposed a method of regulating the bias of the belt (see, for example, Japanese Patent Application Laid-open No. 2002-323821).
Specifically, a protective cap made of a resin normally driven to rotate by the frictional contact thereof with the outer peripheral surface of the end portion of the belt is provided so as to cover the end portion of the belt, and the movement of this protective cap made of a resin toward the belt is regulated by a fixed flange.
However, in the case of such a method of regulating the bias of the belt, because of a construction in which the protective cap made of a resin restrains the configuration of the belt, there has been the possibility of a load being applied to the belt to thereby damage the belt.
Also, when an attempt is made to achieve the higher speed of the image forming apparatus, the construction in which the outer peripheral surface of the belt and the protective cap made of a resin frictionally slide with each other has led to the possibility of the belt being damaged with the shaving of the surface layer of the belt.